This invention relates to a structural framework, a method of forming a framework and webs therefor and, in particular, but not exclusively, to a structural framework in the form of a building truss including at least one top chord arranged obliquely to a generally horizontal bottom chord. The invention also relates to a pedestal for use in the manufacture of such frameworks.
Our International Patent Application No. PCT/US00/23367 discloses a structural framework in the form of a building truss which includes metal web members which extend between the top chords of the truss and the bottom chord of the truss. The reinforcing web members in one form as disclosed in the above International application comprise tubular members of circular cross section which have deformed ends to provide flattened tabs which extend parallel to the longitudinal axis of the web member. The tabs are bent during installation so as to lie flush with a surface of the chords to which the reinforcing members are to be connected. In conventional wooden trusses, adjacent reinforcing web members are arranged so that the web members contact one another. Indeed, in the formation of conventional trusses which have wooden reinforcing web members, the web members contact one another so that compressive and tensile loads applied to the truss are transferred from the chords and absorbed by the truss. In general practice the wooden web member which is to undergo compression contacts the adjacent web member which undergoes tension and the two web members are connected to a chord of the truss by a common connector plate.
In the formation of conventional structural frameworks, in particular, wooden trusses which have oblique top chords and a generally horizontal bottom chord, the chords are laid out on pedestals which are positioned to define the general configuration of the truss. The chords can be held in place by clamps which abut outer surfaces of the chords. Reinforcing web members cut from wood are connected to the chords at predetermined locations and the prescribed length of the wooden reinforcing web members and their proper installation in the truss define the final configuration of the truss. In particular, the wooden members are generally cut to have an end face at each end and the end face of a web member is positioned at a predetermined location and secured to a chord. The other end face is then pulled into engagement with an opposed chord until the end face sits flush with the opposed chord thereby indicating that the web member is in position. This may require some movement of the chord so that the chord does sit flush with the end of the web member. Such movement may be necessary to take a bow out of the chord. When the end is positioned flush with the chord, the end is secured in position. Thus, the final exact shape of the framework and, in particular, the chords of the framework is provided by the installation of the reinforcing web members in the framework.
In the formation of structural frameworks in which metal web members are used, the manner of connecting the metal web members, as described in the above International application, does not allow the installation of the web members themselves to define the configuration of the truss.
Furtherstill, in conventional frameworks which have wooden web members, the web members are laid out and secured in order because of the need to abut adjacent web members together. This therefore requires a workman to work in a particular sequence and the workman does not have the luxury of installing any particular web member at any particular time.
The object of the invention is to provide improvements to the structural frameworks and their method of manufacture disclosed in the above International application and also to the conventional wooden trusses.
The invention in a first aspect provides a method of forming a structural member having at least one top chord and at least one bottom chord, including the steps of:
defining a theoretical connection point on at least one of the chords which provides structural integrity of the framework;
connecting the metal web member to the bottom chord and to the top chord so that the web member is connected to the said one of the bottom chord or the top chord at a web member connection point spaced from the theoretical connection point.
The formation of the structural framework with web members connecting the bottom chord and spaced from the theoretical connection point by a predetermined distance, enables greater flexibility in the selection of metal web members because adjacent web members do not have to be, and in fact are not, in actual physical contact with one another. Thus, web members from a stock set of web member lengths are more easily selected for use in the truss and more easily assembled in the truss because of the ability to space the connection points of the web members from a theoretical connection point by a predetermined distance.
Preferably the method includes connecting a plurality of web members between the top chord and bottom chord so that the web members are inclined with respect to the chords and define pairs of web members which have a first end which are closer to one another than a second end of the web members of each pair, and wherein the said first ends are both connected to one of the chords at web member connection points which are spaced apart from the theoretical connection point with the theoretical connection point being between the web member connection points of the first ends of the web members.
Preferably the step of connecting the web members at the web member connection points comprises spacing the web member connection points apart from the theoretical connection point by a predetermined distance.
Preferably the step of spacing the web member connection points apart by the predetermined distance comprise connecting the chords to the bottom truss within a predetermined distance range from the theoretical connection point but not outside the predetermined distance range.
Preferably the method includes the step of providing support means on which the chords are supported and the pedestals having markings which define the predetermined distance range in which the reinforcing web members can be connected to the web member.
Preferably the method includes the step of providing the reinforcing web member with tabs which are bent with respect to the longitudinal axis of the web member at an oblique angle with respect to the longitudinal axis of the web member, locating a tab against a surface of one of the chords and securing the tab to the chord, manually pulling the web member so as to bring the tab at the other end of the web member into engagement with another of the chords and to cause the said tabs to further bend so as to sit flush with the chords, and securing the other of the tabs in position.
Preferably the step of securing the web members includes providing temporary connection means on at least the said other tab so that when the said other tab is pulled into engagement with the other chord, the ancillary connection means temporarily connects and holds the reinforcing web member in position to facilitate final securement of the other said tab to the other said chord. Preferably the step of providing ancillary connection means comprises providing a barb on the web member which engages and penetrates the chord to temporarily locate and hold the web member in position.
Preferably the barb is formed by bursting a hole through the tab, or forming a tooth on the tab adjacent an edge portion of the tab.
Preferably the support means comprises at least one pedestal. However, in other embodiments the support means could comprise a support table or platform with moveable support elements.
The invention may also be said to reside in a method of forming a structural framework having at least one top chord and at least one bottom chord, including the steps of:
providing support means for supporting the chords of a framework, with the support means including markings which define connection regions at which ends of reinforcing web members can be connected to the chords of the framework;
laying the at least one top chord and the bottom chord on the support means; and
connecting the reinforcing web members between the at least one top chord of the framework and the bottom chord of the framework by securing the ends of the reinforcing web members within the connection regions marked on the support means.
Preferably the step of providing support means comprises the step of moving the support means to predetermined positions so as to define the connection regions of the reinforcing web members to the chords when the chords are laid on the support means.
Preferably the step of providing the markings includes providing a marking which defines a theoretical connection point, and a marking which defines, with a theoretical connection point, the connection region.
Preferably the step of providing the markings further includes providing a marking which defines a preferred connection point between the theoretical connection point and the marking which defines the connection region with the theoretical connection point.
Preferably the support means comprises at least one pedestal. However, in other embodiments the support means could comprise a support table or platform with moveable support elements.
Preferably the method includes the step of providing the reinforcing web member with tabs which are bent with respect to the longitudinal axis of the web member at an oblique angle with respect to the longitudinal axis of the web member, locating a tab against a surface of one of the chords and securing the tab to the chord, manually pulling the web member so as to bring the tab at the other end of the web member into engagement with another of the chords and to cause the said tabs to further bend so as to sit flush with the chords, and securing the other of the tabs in position.
Preferably the step of securing the web members includes providing temporary connection means on at least the said other tab so that when the said other tab is pulled into engagement with the other chord, the ancillary connection means temporarily connects and holds the reinforcing web member in position to facilitate final securement of the other said tab to the other said chord.
Preferably the step of providing ancillary connection means comprises providing a barb on the web member which engages and penetrates the chord to temporarily locate the web member in position.
Preferably the barb is formed by bursting a hole through the tab, or forming a tooth on the tab adjacent an edge portion of the tab.
The invention may also be said to reside in a support member for supporting a chord of a structural framework, the support member including:
an upper support region for supporting the chord; and
markings on the upper support portion for defining at least one connection region in which a reinforcing web member of the structural framework can be connected to a chord of the framework when the chord is supported on the support member.
Preferably the markings include a first marking which shows a theoretical connection point and a second marking which shows a desired connection point.
Preferably the markings further include a third marking which defines, with the first marking, the connection region.
Preferably the support member comprises a pedestal for coupling with a rail member on which the pedestal can move from one place to another.
The invention, in a further aspect, may be said to reside in a structural framework including:
at least one top chord;
at least one bottom chord;
at least two adjacent metal web members extending between the top chord and the bottom chord, the adjacent web members each having a respective end connected to one of the chords so that the respective ends are spaced apart from one another, and with the end of one of the web members being connected to the chord a first distance spaced from a theoretical connection point and the end of the other web member being connected to the chord a second distance spaced from the theoretical connection point, the theoretical connection point being between the two ends of the respective web members which are connected to the chord, and so that the adjacent web members do not abut one another.
This aspect of the invention provides considerably greater freedom in connecting the web members to the chords because the web members do not need to abut one another, but rather are spaced on either side of a theoretical connection point which is used in analysis of the framework design to determine where web members should be located in order to provide the required structural integrity of the framework. Since the web members do not abut one another, the web members can therefore be laid out in any particular order and can be connected in any sequence. This provides a workman or workmen with greater freedom in connecting ends of the chords and therefore provides for the possibility of greater productivity in that frameworks can be assembled much quicker than in the past.
Preferably the first distance is the same as the second distance.
Preferably the ends of the web members are connected to the chord at predetermined web member connection points spaced from the theoretical point.
Preferably the web members are connection to the chords within a connection range which includes the preferred web member connection point for each of the respective web members.
Preferably the web members include tabs which sit flush with a surface of the chord and the tabs are connected to the chord by screws which pass through a hole in the tab.
Preferably the hole defines the connection point of the respective web members to the chord.
A further aspect of the present invention is directed to defining the final configuration of the chords of a framework which is to have metal reinforcing web members.
A further aspect of the invention may therefore be said to reside in a method of forming a structural framework having at least one top chord and at least one bottom chord, including the steps of:
laying the top chord and the bottom chord on one or more support members;
clamping inner surfaces of the chords against an abutment located adjacent an outer surfaces of the chords so as to define the final configuration of the top chord and the bottom chord of the framework; and
securing metal reinforcing members between the top chord and the bottom chord.
During the installation step of the reinforcing web members, ends of the reinforcing web members are secured to surfaces of the chords by driving a screw through the reinforcing web members and into the surfaces of the chords. This step tends to pull the chords inwardly and inward movement of the chords which, if the chords were not clamped from the inner surfaces, could cause a deformation of the chords. Since the inner surfaces of the chords are clamped, the chords are prevented from deforming and therefore do not change their required geometrical configuration during installation of the reinforcing web members.
In the preferred embodiment, the reinforcing web members are secured so that the web members connect with the chords at a prescribed distance from a theoretical connection point. This aspect of the invention has particular application to this preferred embodiment because if the chords are connected at positions away from the theoretical connection point, it is completely impossible, unless the inner surfaces of the chords are clamped and prevented from moving, to ensure that installation of the web members will define the correct geometrical shape of the structural framework. Thus, by clamping the inner surfaces so that the geometrical shape of the framework is determined and fixed before the web members are installed, the geometrical shape does not change during installation of the web members regardless of how or where the web members are connected to the chords.
A further aspect of the invention may be said to reside in a method of forming a structural member having at least one top chord and at least one bottom chord, the method including the steps of:
providing a metal reinforcing web member having connection tabs at each end with at least one of the connection tabs having an ancillary connection means;
securing one of the tabs to one of the chords;
moving the reinforcing web member so that the other of the tabs, which includes the or one of the ancillary connection means, is brought into engagement with the other of the chords and so that the ancillary connection means connects to the chord and temporarily holds the reinforcing member in position; and
connecting the other of the tabs to the other of the chords to permanently secure the other tab to the other chord.
This aspect of the invention enables the reinforcing web members to be pulled into engagement with the chords and for the ancillary connection means to hold the chord in position so the web member can be fully released by a workman and the workman then has two free hands to permanently secure the other of the tabs in position. Thus, it is not necessary for the workman to hold the reinforcing web member in position and use one hand to secure the tab or for two workmen to perform this operation. Furtherstill, since the tab is connected to the chord and held in place by the ancillary connection means, the reinforcing web member and tab can be properly located in position and will hold that position until the tab is permanently connected to the chord. This prevents the reinforcing web member from moving slightly if it is released which would change its position from that at which the workman intends to secure the tab. Thus, the tab can therefore be more easily located in position and flush with a surface of the chord and the reinforcing web member tightly and accurately secured in position.
Preferably the step of temporarily locating the other tab in position by the ancillary connection means comprises the step of locating the tab in position so that the ancillary connection means penetrates the chord to hold the chord in place.
Preferably the step of providing the other tab with the ancillary connection means comprises providing the tab with at least one barb which can penetrate a chord to hold the tab in position.
Preferably the step of providing the barb comprises providing the barb by forming a burst hole through the tab, or forming a tooth on a side edge of the tab.
This aspect of the invention may also be said to reside in a metal reinforcing web member for a structural framework, said web member including:
a web member body;
at least one securement tab at one end of the web member body; and
ancillary connection means on the reinforcing web member for holding the tab in position when the reinforcing web member is located in position in the framework to enable a workman to permanently secure the tab to the chord.
Preferably the reinforcing web member has tabs at each end and each tab is provided with a said ancillary connection means.
In one embodiment the ancillary connection means may be provided by at least one barb on the tab.
The barb may be provided by a burst hole with the barb comprising metal which is deformed from the tab during formation of the burst hole.
In another embodiment the barb may be provided in the form of a tooth arranged at a side edge of the tab.
A further aspect of the invention may be said to reside in a metal reinforcing web member for use in a structural framework, said web member including:
a web member body;
at least one flattened tab formed at one end of the web member body;
the web member body being formed from a tube of metal having free edges which are adjacent one another and which define therebetween a longitudinal slot; and
a deformation forming a transition from the web member body to the tab, the deformation including a valley and the valley being aligned with the longitudinal slot in the web member body.
Preferably the valley includes a slit formed by forcing the free edges in the vicinity of the deformation away from one another during formation of the valley, the slit being a continuation of the said slot.
Preferably the slit includes a wide central portion which tapers towards a first end adjacent the slot and towards a second end adjacent the tab.
A further aspect of the present invention may also be said to reside in a reinforcing web member for a structural framework, the reinforcing web member including:
a web member body;
at least one connection tab at one end of the web member body; and
the connection tab being bent at an oblique angle with respect to the longitudinal axis of the web member body before installation of the web member into the framework.
Preferably both ends of the web member body include connection tabs and one of the said tabs is bent to the predetermined oblique angle in one direction and the other of the tabs is bent to the predetermined oblique angle in an opposite direction.
Preferably the predetermined oblique angle is an angle of about 30xc2x0 with respect to the longitudinal axis of the web member body.
Preferably the web member body is circular in transverse cross section.
Preferably the tab is formed by deforming the end of the web member so as to form a flattened tab and a transition region extending from the tab to the web member body, the transition region including a pressed valley extending between two ridges.
Preferably the transition section includes a pair of opposed valleys defined between a respective pair of ridges.
Preferably the tabs include a punched hole for receiving a fastener to secure the tabs to chords of the structural framework.
Preferably the tab includes ancillary connection means for temporarily holding the tab and therefore the reinforcing web member in position during installation of the reinforcing web member in the structural framework.
Preferably the ancillary connection means includes at least one barb formed on the tab.
Preferably the at least one barb is formed by forming a burst hole with the barb being material deformed during the formation of the burst hole.
In another embodiment the barb comprises a tooth formed on an edge portion of the tab.
Preferably, according to each of the aspects of the invention described above, the framework comprises a framework having a bottom chord and at least one top chord which is arranged obliquely with respect to the bottom chord.